Scott,
That is correct about the gain knob, it is not a volume knob, so it doesn’t reduce volume. The circuit itself, does have a slight drop in amplitude when the gain knob is at fully the counterclockwise position, but it’s only a few dBs. The opamp circuits in the pedal are non-inverting, so they cannot lower gain, the lowest they can go is unity. But I’m not sure that lowering the volume/gain level of the pedals is going to solve your problem. It sounds like you are asking for a wider dynamic range of the pedal, which lowering the gain setting will not give you.
You can test if this by adding another pedal (with a volume control) to the effects loop after the VPM-1, and with that pedal set to unity gain, adjust its volume control lower. This will at least give you an idea of weather lowering the VPM-1’s output gain will solve your problem. If that helps the problem you are experiencing, then you could modify the voltage divider circuit on the VPM-1’s output. I can tell you what resistor to change when and if that time comes.
I think what will work better for you is if you do what i was suggesting in the previous post about setting the treadle calibration differently. If you set it to where the volume on the VPM-1 is at 25% in the heal down position, then set the preamp on the amp for a nice sound at a quiet level. Then you’ll have the entire range of treadle movement to turn up the amp. You are already using the VPM-1 in this way, where you get a sound that you like in the heal down position, but if you set up the calibration this way you won’t hear the noise artifacts at the low end of the treadle position anymore.
-Brach